Brownsnout Spookfish – 4-Eyed Fish WIth Mirrors For Lenses
The brownsnout spookfish, a bizarre “four-eyed” fish, has been identified as the only backboned creature known to use mirrors rather than lenses to get images into focus. The brownsnout spookfish, Dolichopteryx longipes, has ordinary eyes with lenses pointing upwards, but alongside them are downward-looking eyes fitted with tiny mirrored plates. The plates, thought to be made of guanine crystals, are arranged so that the light entering the eye is reflected to a focused point on the retina, allowing the fish to see what lurks below it.
The mirrors allow the fish to detect flashes of light made by creatures in the deep in more detail than would be achieved by eyes with lenses, giving it an early warning of predators. Mirrors are better at providing focused images in the deep sea because they are more efficient in the low light levels and they avoid imperfections in images created by lenses. Brownsnout spookfish were discovered 120 years ago but little was known about them until one was pulled up from 2,000-2,600ft (600-800m) during a scientific trawl in the Tonga Trench in the southern Pacific 18 months ago. It was the first live specimen to be studied by researchers. [Via]
